Many types of electronic instruments provide for manual input of data or information through operator settable switches. The settings of these switches are then read by the related electronic equipment. Very often the information input through these switches is critical to the correct operation of the instrument or apparatus. Hence, it is important to determine as quickly as possible whether or not the switch settings which are being sensed represent reliable information.
One type of commonly used operator settable switch is a thumb wheel switch which converts a switch position to a binary coded decimal (BCD) code which can then be subsequently converted to binary for arithmetic or logic operations. While such switches are reasonably reliable they do from time to time malfunction and generate an incorrect set of electrical signals for a given switch position. Additionally, while the reading and addressing electronics utilized in connection with such switches are also fairly reliable, they too malfunction, from time to time.
There is thus a continuing need for an inexpensive apparatus and method, which will enable an associated electronic circuit to determine whether or not the information being sensed from a manually settable switch or switches is reasonably likely to have been correctly generated by the switches.